COMP 3000 Essay 1 2010 Question 4

Question

What "operating systems" have been implemented in the following languages: LISP, Modula-3, Smalltalk, Java? To what extent do these systems match the capabilities of operating systems implemented in C and C++?

Team Note (to be removed by delivery date)

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Answer

Introduction

Not so long ago people believed the Earth was a flat world at the center of the universe. This essay addresses a more recent falsehood: that all operating systems are written in assembly language and C. It's not surprising that students of computing in this century would genuflect at the academic altars of Kernighan & Ritchie. After all we grew up with our computer worlds already pre-formed into the conceptual continents of Apple OS, UNIX, and Windows. The more historically curious among us are vaguely aware that other island cultures do exist but they represent civilizations defeated in the marketplace. Explorations into these ancient worlds resemble documentaries about archeologists decoding rediscovered languages etched in stone. But scratch the surface of any of our so-called modern operating systems and you'll find echoes of these ancient languages in our own familiar worlds. Ellen Ullman said it best when she wrote,

We build our computer systems like we build our cities: over time, without a plan, on top of ruins.

In the sections below we present our explorations into a few truly foundational operating systems. We will also see some brand new ones that prove we stand, as one twelfth century scholar put it, on the shoulders of giants.

The following is a short list of operating systems written partially or completely with the given language. We will go into more detail in the language-specific sections below.

Operating Systems By Language

Language	OS List
Lisp	MIT's Lisp Machines, Genera
Modula-3	SPIN OS
Smalltalk	Smalltalk-80 on Xerox Alto, Squeak
Java	JavaOS, JNode, JX, Android

Java Based

Overview

Java is used on a plethora of devices and systems throughout the industry from cell phones to web applets. With Java being a language that creates a virtual machine for each application, one would think that it is already suited to be an operating system in itself but this is not the case. Java is built to run on top of other operating systems such as Microsoft Windows, Mac OS X and Ubuntu Linux rather than being a standalone system. This section will discuss various operating systems that are written in Java such as JavaOS, Android, JNode and JX.

JavaOS is Sun Microsystems very own creation. This system runs on different layers to make a scalable and easily updateable operating system ^[1]. The first layer is the microkernel which handles the memory architecture, booting, interrupt handling, threading, traps and DMA handling. The Java Virtual Machine is also compiled into native code for the system and is run on top of the microkernel. The second layer consists of the JavaOS for Business software which extends the memory module to optimize for systems with limited memory^[2]. All device drivers for the system are written and run in Java and are what the third layer is consisted of. Finally, the fourth layer is a stand-alone JDK runtime environment used to run user applications.

Android was created by a very ambitious team at Google for use with cell phones. It is basically an operating system running on top of another minimalistic operating system. At the very lowest end of Android, a Linux 2.6 kernel is what powers it. All device drivers are written and compiled for the native hardware or compiled using Google’s Native Development Kit and core system libraries such as libc, OpenGL | ES and SQLite are dynamically linked in per application ^[3]. In the Android runtime, the Dalvik Virtual Machine (DVM) controls applications similar to the Java Virtual Machine. Dalvik is similar to the aforementioned JavaOS as it relies on the kernel to manage threading and low-level memory management. Running on top of the DVM are core libraries and application frameworks for the Android operating system. These frameworks include resource management, window management, notification manage just to name a few. Applications are then built on top of these frameworks and are the end result in which the user will actually interact with.

JNode began as the Java Bootable System (JBS) in 1995. Ewout Prangsma, the creator, was unhappy with the amount of native C and assembly used for the system so he began a new project, JNode. JNode only uses a small amount of assembly code for booting the system now compared to the initial JBS ^[4]. The rest of the system is completely written in Java including its graphical user interface. Applications in JNode are referred to as plugins ^[5] including the device drivers, filesystems, networking and user applications.

JX was created at the University of Erlangen. At it’s base is a microkernel that the basic Java Virtual Machine runs on which is similar to JavaOS. The system runs on the idea of domains where the microkernel runs at domain level zero and subsequent programs run in domain A, B, C, etc. Domains contain their own threads, heap and garbage collector and can communicate with other domains using portals. A portal is essentially the same as inter-process communication but using domains as processes instead ^[6].

Motivation

Java is a powerful language that already contains the code necessary for running on many different platforms. With the concept of virtual machines for each individual application it provides a layer of security that not every operating system has. Each virtual machine has it’s own heap and with the use of just-in-time (JIT) compilers can almost achieve comparable run times when compared to native compiled applications.

Since all Java applications are compiled into the same set of bytecode, third-parties can develop their own implementation of the Java runtime. For example, Google has created the Dalvik Virtual Machine for use with the Android platform so it will run more efficiently on small devices while reducing the memory footprint ^[7]. Google has just recently released Android 2.2 which includes a new JIT compiler for their Dalvik Virtual Machine which can improve speeds of applications up to 2-5 times ^[8]. IBM also has their own version of the Java Virtual Machine, J9, that is used in many of their own pieces of software and also includes its own implementation of a JIT compiler.